Devices such as directional drills are used in industry to bore openings underground for pipes, cables, etc. Directional drills typically use a number of sections to form a drill stem. The sections are inserted one at a time during a forward drilling operation, and are removed one at a time after the bore has reached a desired depth in order to remove the drill stem from the bore. Although an example of a directional drill is used in the following descriptions, other ground drills utilizing a number of sections of drill stem are also contemplated to be within the scope of the invention.
Sections of drill stem are typically joined together using a mating threaded joint. In this configuration, several sections of drill stem can be housed in a small space, for example in a hopper on a drill device. Drilling devices such as a directional drill are configured with gripping devices to selectively hold the sections of drill stem during a joining or detaching operation to add or remove sections of the drill stem.
A problem with current gripping device designs is that they are large and cumbersome. Existing configurations use a pair of hydraulic cylinders for a single drill gripping device, which is expensive to manufacture, and adds size and weight to a cumbersome drilling device. Further, existing drill gripping devices do not center well on a section of drill stem during a gripping operation. A poorly centered gripping device leads to excessive wear of gripping jaws, among other problems.
What is needed is a drill gripping device that is smaller and less expensive to manufacture. What is also needed is a drill gripping device with improved operation characteristics such as extended jaw life.